The invention is in the field of conveying large quantities of loose material, such as dirt, rocks or other granular material, into an elongated container, such as a railroad hopper car, for transport of the material to a dump site. The invention is particularly useful in railroad right-of-way maintenance, including cleaning-out ditches along the right-of-way and removing old ballast from beneath the rails and ties of a track.
In such applications, high volume and weights of material must be handled and temporarily stored in large containers, most typically a series of railroad hopper cars connected to form a train, and transported to a dump or discharge site. Because of the elongated nature of a railroad car, provision must be made for discharging the material into the car reasonably uniformly throughout the length of the car for maximum utilization of carrying capacity and provision must be made for efficient dumping of the car at the dump site. Other requirements peculiar to this field include addressing the need for unifoirm discharge from both sides of a conveyor belt into a railroad car, particularly when the car is on a super elevated curve in the track thereby resulting in tilting the conveyor and car toward the inside of the curve and creating a tendency for all material to be discharged from the lower side of the conveyor belt, thereby overloading the car on one side. An additional requirement is efficient dumping, which is best achieved by side dumping each car at the dump site. Side dumping alters the center of gravity of the loaded car during the dumping operation. Additional shifting of the center of gravity occurs if the conveyor structure is tipped to one side as the hopper is tipped for side dumping, which occurs if the conveyor structure is mounted directly to the hopper. The combined weight shift of the material, the railroad hopper structure and the conveyor structure causes unstable conditions and leads to tipping the car off the tracks, an obviously undesirable result, unless tie-down steps are taken.
Prior art apparatus has been constructed with the conveyor structure mounted directly to the side-dumping hopper. In the prior art the stability problem has been addressed by requiring tie down of the wheels of a car being side dumped on the side opposite the discharge side to prevent roll over. This is an unsatisfactory solution, however, because of the extra labor and tie-down apparatus required, and it is dependent on the ability to achieve a secure tie down, which is not always possible. The problem of non-uniform discharge from the respective sides of the conveyor belt when the conveyor is tilted when the railroad car is on a super elevated curve has not been addressed by any prior art apparatus known to applicants.
O'Leary U.S. Pat. No. 3,355,041 teaches a train-like series of hopper tubs and scraper means for loading consecutive tubs, but fails to address the problems described above.